#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <stdio.h>

#define CLEARBITS(a,b)   ((a) &= ~(b))
#define SETBITS(a,b)     ((a) |= (b))
#define ISSET(a,b)       (((a) & (b))!=0)
#define ISCLEARED(a,b)   (((a) & (b))==0)

#ifndef MAX
#define MAX(a,b)  (((a) > (b)) ? (a) : (b))
#endif              /* max */

#ifndef MIN
#define MIN(a,b)  (((a) < (b)) ? (a) : (b))
#endif              /* min */

#define MY_90K_COUNTS_OF_1_SECOND  90000

#define MY_SEARCH_PCR_SIZE  ((200 * 1024 / 188) * 188)

#define MY_RB16(x)  ((((const unsigned char*)(x))[0] << 8) | ((const unsigned char*)(x))[1])

#define MY_RB32(x)  ((((const unsigned char*)(x))[0] << 24) | \
                     (((const unsigned char*)(x))[1] << 16) | \
                     (((const unsigned char*)(x))[2] <<  8) | \
                      ((const unsigned char*)(x))[3])

static int MY_ParsePcr( long long *ppcrHigh, int *ppcrLow, const unsigned char *packet )
{
 int afc, len, flags ;
 const unsigned char *p ;
 unsigned int v ;

 afc = (packet[3] >> 4) & 3;
 if(afc <= 1)
   {
    return -1;
   }
 p = packet + 4;
 len = p[0];
 p++;
 if(len == 0)
   {
    return -1;
   }
 flags = *p++;
 len--;
 if(!(flags & 0x10))
   {
    return -1;
   }
 if(len < 6)
   {
    return -1;
   }
 v = MY_RB32(p);
 *ppcrHigh = ((long long)v << 1) | (p[4] >> 7);
 *ppcrLow = ((p[4] & 1) << 8) | p[5];
 return 0;
}

static long long MY_GetPcr( int pcrPid, unsigned char* address, int length, int direction )
{
 int pos ;
 unsigned char* buf ;
 long long timestamp ;
 int pcrL ;

 if( direction == 0 )
   {
    pos = 0 ;
    for(;;)
       {
        if( pos >= length )
          {
           return AV_NOPTS_VALUE ;
          }
        buf = address + pos ;
        if((pcrPid < 0 || (MY_RB16(buf + 1) & 0x1FFF) == pcrPid) &&  MY_ParsePcr(&timestamp, &pcrL, buf) == 0)
          {
           break;
          }
        pos += 188 ;
       }
    return timestamp ;
   }
  else
   {
    pos = ((length/188)*188) - 188 ;
    for(;;)
       {
        if( pos < 0 )
          {
           return AV_NOPTS_VALUE ;
          }
        buf = address + pos ;
        if((pcrPid < 0 || (MY_RB16(buf + 1) & 0x1FFF) == pcrPid) &&  MY_ParsePcr(&timestamp, &pcrL, buf) == 0)
          {
           break;
          }
        pos -= 188 ;
       }
    return timestamp ;
   }
}

int main(int argc, char *argv[])
{
 AVFormatContext *pFormatCtx ;
 int             i ;
 int             videoStream ;
 AVPacket        packet ;
 AVCodecContext  *pCodecCtx;
 AVCodec         *pCodec;
 AVFrame         *pFrame;
 AVFrame         *pFrameRGB;
 int             numBytes;
 unsigned char   *buffer;

 if(argc < 2)
   {
    printf("Please provide a movie file\n");
    return -1;
   }

 // Register all formats and codecs
 av_register_all();

 // Open video file
 if(av_open_input_file(&pFormatCtx, argv[1], NULL, 0, NULL)!=0)
   {
    return -1; // Couldn't open file
   }

 //printf("pFormatCtx->nb_streams:%d\n",pFormatCtx->nb_streams);

 // Retrieve stream information
 if(av_find_stream_info(pFormatCtx)<0)
   {
    return -1; // Couldn't find stream information
   }

 // Dump information about file onto standard error
 dump_format(pFormatCtx, 0, argv[1], 0);

 //printf("pFormatCtx->nb_streams:%d\n",pFormatCtx->nb_streams);

 // Find the first video stream
 videoStream = -1 ;
 for( i = 0 ; i < pFormatCtx->nb_streams ; i ++ )
    {
     if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO)
       {
        videoStream=i;
        break;
       }
    }

 if( videoStream == -1 )
   {
    printf("Didn't find a video stream.\n");
    return -1; // Didn't find a video stream
   }

 // Get a pointer to the codec context for the video stream
 pCodecCtx=pFormatCtx->streams[videoStream]->codec;

 // Find the decoder for the video stream
 pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
 if(pCodec==NULL) {
   printf("Unsupported codec!\n");
   return -1; // Codec not found
 }
 // Open codec
 if(avcodec_open(pCodecCtx, pCodec)<0)
   return -1; // Could not open codec

 // Allocate video frame
 pFrame=avcodec_alloc_frame();

 // Allocate an AVFrame structure
 pFrameRGB=avcodec_alloc_frame();
 if(pFrameRGB==NULL)
   return -1;

 // Determine required buffer size and allocate buffer
 numBytes=avpicture_get_size(PIX_FMT_RGB24, pCodecCtx->width,
           pCodecCtx->height);
 buffer=(unsigned char *)av_malloc(numBytes*sizeof(unsigned char ));

 // Assign appropriate parts of buffer to image planes in pFrameRGB
 // Note that pFrameRGB is an AVFrame, but AVFrame is a superset
 // of AVPicture
 avpicture_fill((AVPicture *)pFrameRGB, buffer, PIX_FMT_RGB24,
     pCodecCtx->width, pCodecCtx->height);

 url_fseek( pFormatCtx->pb, 0, SEEK_SET);
 unsigned char pktBuf[188] ;
 long long pcr ;
 while( get_buffer( pFormatCtx->pb, pktBuf, 188) > 0 )
      {
       pcr = MY_GetPcr( pFormatCtx->streams[videoStream]->id, pktBuf, 188, 0 );
       if( pcr != AV_NOPTS_VALUE )
         {
          printf("pcr: %lld\n",pcr);
         }
      }

 // Free the RGB image
 av_free(buffer);
 av_free(pFrameRGB);

 // Free the YUV frame
 av_free(pFrame);

 // Close the codec
 avcodec_close(pCodecCtx);

 // Close the video file
 av_close_input_file(pFormatCtx);

 return 0;
}